668 research outputs found
The changing incentive structure of institutional asset managers: implications for financial markets.
This article presents the principal findings of the Working Group on Incentive Structures in Institutional Asset Management set up under the aegis of the Commitee on the Global Financial System (CGFS). These findings, which have recently been published in a report, aim to give the central bank community â and beyond that, the financial community â a better understanding of ongoing developments in the fund management industry and their potential implications for financial markets. The report, based on a comprehensive literature review and extensive interviews with market practitioners, has identified various features and trends in the industry with a potential effect on the functioning of financial markets. However, as many of these effects are at least partially offsetting, the lack of reliable empirical evidence has not allowed the working group to come to a clear-cut conclusion on the aggregate effect of these various features and trends at the current juncture. Still, one broad conclusion may be drawn from this report: ongoing and future developments in the fund management industry have the potential to change institutional behaviour in ways that can be important for financial markets. This relates to the general issue of preserving the diversity of investment behaviour, and partially results from the fact that parts of the institutional asset management industry have moved towards becoming a «commodity» industry offering investors more and more standardised investments products and approaches. Therefore, developments in the industry may require further attention by the financial community as a whole. More specifically, the report points to four broad areas where particular attention should be paid: risk management and disclosure, conflicts of interest, explicit and implicit barriers to market entry, and regulatory trade-offs.
Radio emission of the Galactic X-rays binaries with relativistic jets
Variable non-thermal radio emission from Galactic X-ray binaries is a trace
of relativistic jets, created near accretion disks. The spectral
characteristics of a lot of radio flares in the X-ray binaries with jets (RJXB)
is discussed in this report. We carried out several long daily monitoring
programs with the RATAN-600 radio telescope of the sources: SS433, Cyg X-3,
LSI+61o303, GRS 1915+10 and some others. We also reviewed some data from the
GBI monitoring program at two frequencies and hard X-ray BATSE (20-100 keV) and
soft X-ray RTXE (2-12 keV) ASM data. We confirmed that flaring radio emission
of Cyg X-3 correlated with hard and anti-correlated with soft X-ray emission
during the strong flare (>\tau$ depends upon frequency as tau \propto \nu^{-0.4} in the first
flare and does not depend upon frequency in the second flare, and is equal to
\tau=6+-1 days at frequencies from 0.96 to 21.7 GHz in the last flare in May
1999. Many flaring RJXB show two, exponential and power, laws of flare decay.
Moreover, these different laws could be present in one or several flares and
commonly flare decays are faster at a higher frequency. The decay law seems to
change because of geometric form of the conical hollow jets. The synchrotron
and inverse Compton losses could explain general frequency dependences in flare
evolution. In conclusion we summarized the general radio properties of RJXB.Comment: 10 pages, LaTeX, 14 Postscript figures, talk given at the Gamov
Memorial International Conference (GMIC'99) "Early Universe: Cosmological
Problems and Instrumental Technologies" in St.Petersburg, 23-27 August, 1999,
to appear in Astron. Astrophys. Trans., 200
LOFT as a discovery machine for jetted Tidal Disruption Events
This is a White Paper in support of the mission concept of the Large
Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We
discuss the potential of LOFT for the study of jetted tidal disruption events.
For a summary, we refer to the paper.Comment: White Paper in Support of the Mission Concept of the Large
Observatory for X-ray Timin
A transient relativistic radio jet from Cygnus X-1
We report the first observation of a transient relativistic jet from the
canonical black hole candidate, Cygnus X-1, obtained with the Multi-Element
Radio-Linked Interferometer Network (MERLIN). The jet was observed in only one
of six epochs of MERLIN imaging of the source during a phase of repeated X-ray
spectral transitions in 2004 Jan--Feb, and this epoch corresponded to the
softest 1.5-12 keV X-ray spectrum. With only a single epoch revealing the jet,
we cannot formally constrain its velocity. Nevertheless, several lines of
reasoning suggest that the jet was probably launched 0.5-4.0 days before this
brightening, corresponding to projected velocities of 0.2c < v_app < 1.6c, and
an intrinsic velocity of > 0.3c. We also report the occurrence of a major radio
flare from Cyg X-1, reaching a flux density of ~120 mJy at 15 GHz, and yet not
associated with any resolvable radio emission, despite a concerted effort with
MERLIN. We discuss the resolved jet in terms of the recently proposed 'unified
model' for the disc-jet coupling in black hole X-ray binaries, and tentatively
identify the 'jet line' for Cyg X-1. The source is consistent with the model in
the sense that a steady jet appears to persist initially when the X-ray
spectrum starts softening, and that once the spectral softening is complete the
core radio emission is suppressed and transient ejecta / shock observed.
However, there are some anomalies, and Cyg X-1 clearly does not behave like a
normal black hole transient in progressing to the canonical soft / thermal
state once the ejection event has happened.Comment: Accepted for publication in MNRA
Studying the X-ray hysteresis in GX 339-4: the disc and iron line over one decade
We report on a comprehensive and consistent investigation into the X-ray
emission from GX 339-4. All public observations in the 11 year RXTE archive
were analysed. Three different types of model - single powerlaw, broken
powerlaw and a disc + powerlaw - were fitted to investigate the evolution of
the disc, along with a fixed gaussian component at 6.4 keV to investigate any
iron line in the spectrum. We show that the relative variation in flux and
X-ray colour between the two best sampled outbursts are very similar. The decay
of the disc temperature during the outburst is clearly seen in the soft state.
The expected decay is S_Disc \propto T^4; we measure T^4.75\pm0.23. This
implies that the inner disc radius is approximately constant in the soft state.
We also show a significant anti-correlation between the iron line significant
width and the X-ray flux in the soft state while in the hard state the EW is
independent of the flux. This results in hysteresis in the relation between
X-ray flux and both line flux and EW. To compare the X-ray binary outburst to
the behaviour seen in AGN, we construct a Disc Fraction Luminosity Diagram for
GX 339-4, the first for an X-ray binary. The shape qualitatively matches that
produced for AGN. Linking this with the radio emission from GX 339-4 the change
in radio spectrum between the disc and power-law dominated states is clearly
visible.Comment: Accepted for publication in MNRAS, 20 pages, 17 figures. For high-res
version see http://www.astro.soton.ac.uk/~r.j.dunn/publications.htm
The radio spectrum of a quiescent stellar mass black hole
Observations of V404 Cyg performed with the Westerbork Synthesis Radio
Telescope at four frequencies, over the interval 1.4-8.4 GHz, have provided us
with the first broadband radio spectrum of a `quiescent' stellar mass black
hole. The measured mean flux density is of 0.35 mJy, with a spectral index
alpha=+ 0.09\pm0.19$ (such that S_nu \propto nu^{alpha}). Synchrotron emission
from an inhomogeneous partially self-absorbed outflow of plasma accounts for
the flat/inverted radio spectrum, in analogy with hard state black hole X-ray
binaries, indicating that a steady jet is being produced between a few 10^{-6}
and a few per cent of the Eddington X-ray luminosity.Comment: accepted for publication in MNRA
High-energy gamma-ray observations of the accreting black hole V404 Cygni during its June 2015 outburst
We report on Fermi/Large Area Telescope observations of the accreting black
hole low-mass X-ray binary V404 Cygni during its outburst in June-July 2015.
Detailed analyses reveal a possible excess of -ray emission on 26 June
2015, with a very soft spectrum above MeV, at a position consistent with
the direction of V404 Cyg (within the confidence region and a chance
probability of ). This emission cannot be associated with any
previously-known Fermi source. Its temporal coincidence with the brightest
radio and hard X-ray flare in the lightcurve of V404 Cyg, at the end of the
main active phase of its outburst, strengthens the association with V404 Cyg.
If the -ray emission is associated with V404 Cyg, the simultaneous
detection of keV annihilation emission by INTEGRAL requires that the
high-energy rays originate away from the corona, possibly in a
Blandford-Znajek jet. The data give support to models involving a
magnetically-arrested disk where a bright -ray jet can re-form after
the occurrence of a major transient ejection seen in the radio.Comment: 5 pages, 3 figures, accepted for publication in MNRA
Multiwavelength Observations of GX 339-4 in 1996. I. Daily Light Curves and X-ray and Gamma-Ray Spectroscopy
As part of our multiwavelength campaign of GX 339-4 observations in 1996 we
present our radio, X-ray, and gamma-ray observations made in July, when the
source was in a hard state (= soft X-ray low state). The radio observations
were made at the time when there was a possible radio jet. We show that the
radio spectrum was flat and significantly variable, and that the radio spectral
shape and amplitude at this time were not anomalous for this source. Daily
light curves from our pointed observation July 9-23 using OSSE, from BATSE, and
from the ASM on RXTE also show that there was no significant change in the X-
and gamma-ray flux or hardness during the time the possible radio jet-like
feature was seen. The higher energy portion of our pointed RXTE observation
made July 26 can be equally well fit using simple power law times exponential
(PLE) and Sunyaev-Titarchuk (ST) functions. An additional soft component is
required, as well as a broad emission feature centered on 6.4 keV. This may be
an iron line that is broadened by orbital Doppler motions and/or scattering off
a hot medium. Its equivalent width is 600 eV. Our simplistic continuum fitting
does not require an extra reflection component. Both a PLE and a ST model also
fit our OSSE spectrum on its own. Although the observations are not quite
simultaneous, combining the RXTE and CGRO spectra we find that the PLE model
easily fits the joint spectrum. However, the ST model drops off too rapidly
with increasing energies to give an acceptable joint fit.Comment: Submitted to Astrophysical Journal. 25 pages. 11 figure
Discovery of extended radio emission in the young cluster Wd1
We present 10 micron, ISO-SWS and Australia Telescope Compact Array
observations of the region in the cluster Wd1 in Ara centred on the B[e] star
Ara C. An ISO-SWS spectrum reveals emission from highly ionised species in the
vicinity of the star, suggesting a secondary source of excitation in the
region. We find strong radio emission at both 3.5cm and 6.3cm, with a total
spatial extent of over 20 arcsec. The emission is found to be concentrated in
two discrete structures, separated by 14''. The westerly source is resolved,
with a spectral index indicative of thermal emission. The easterly source is
clearly extended and nonthermal (synchrotron) in nature. Positionally, the B[e]
star is found to coincide with the more compact radio source, while the
southerly lobe of the extended source is coincident with Ara A, an M2 I star.
Observation of the region at 10micron reveals strong emission with an almost
identical spatial distribution to the radio emission. Ara C is found to have an
extreme radio luminosity in comparison to prior radio observations of hot stars
such as O and B supergiants and Wolf-Rayet stars, given the estimated distance
to the cluster. An origin in a detatched shell of material around the central
star is therefore suggested; however given the spatial extent of the emission,
such a shell must be relatively young (10^3 yrs). The extended non thermal
emission associated with the M star Ara A is unexpected; to the best of our
knowledge this is a unique phenomenon. SAX (2-10keV) observations show no
evidence of X-ray emission, which might be expected if a compact companion were
present.Comment: 5 pages including encapsulated figures, figure 3 separate. Accepted
for MNRAS pink page
The Cosmic Battery and the Inner Edge of the Accretion Disk
The Poynting-Robertson Cosmic Battery proposes that the innermost part of the
accretion disk around a black hole is threaded by a large scale dipolar
magnetic field generated in situ, and that the return part of the field
diffuses outward through the accretion disk. This is different from the
scenario that the field originates at large distances and is carried inward by
the accretion flow. In view of the importance of large scale magnetic fields in
regulating the processes of accretion and outflows, we study the stability of
the inner edge of a magnetized disk in general relativity when the distribution
of the magnetic field is the one predicted by the Poynting-Robertson Cosmic
Battery. We found that as the field grows, the inner edge of the disk gradually
moves outward. In a fast spinning black hole with a>0.8M the inner edge moves
back in towards the black hole horizon as the field grows beyond some threshold
value. In all cases, the inner part of the disk undergoes a dramatic structural
change as the field approaches equipartition.Comment: 7 pages, 3 figures, accepted for publication in Monthly Notices of
the RA
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